1. Field of the Invention
This invention relates in general to a riser system that extends between a floating drilling or production platform and a subsea well, and in particular to a union connection at the top of the riser string.
2. Description of the Prior Art
In U.S. Pat. No. 4,403,658, issued Sept. 13, 1983, Bruce J. Watkins, a single stab union is shown for an offshore drilling or production platform. In the patent, at the top of the riser run or string, a termination head is adapted to be received within a female termination housing. The termination housing has a number of radial ports that register with passages located in the termination head. These ports contain high pressure fluid for transmission between the vessel and the subsea well. If it is necessary to disconnect the lower end of the riser from the subsea well temporarily, the termination head can be pulled upward from the termination housing. The lines or hoses connected to the termination housing can remain in place, connected to the housing.
In the Watkins patent, seals are shown around the radial ports and passageways. No details of the structure of the seals are shown, however. The pressures encountered in these passageways can be very high, requiring extremely good seals. The diameters of the seals are fairly large also. The sealing problems are severe also because of the need for sealing on curved mating faces, rather than flat mating faces.